Traditionally, in an image pickup element such as a complementary metal oxide semiconductor (CMOS) image sensor, a plurality of A/D converters (analog digital converter (ADC)) is connected to each output line connected to pixels in each column. The image pickup element has realized data reading at a higher speed by using the plurality of ADCs (for example, refer to Patent Document 1).
Also, there has been an image pickup element, in which a plurality of comparators and counters are mounted to each output line and a voltage of a D/A converter (digital analog converter (DAC)) is shifted by an optional value, which reads a high bit precision signal at a high speed (for example, refer to Patent Document 2).
In addition, there has been an image pickup element which reduces noise and improves a dynamic range by performing A/D conversion twice to a reading signal (for example, refer to Patent Documents 3 and 4).